The automatic update function of WordPress makes it super easy to update the wp-installation. Most of the time
If there’s an update which is not working as requested, you do not need to switch to manual mode and search for your FTP-access on the server immediately. A small trick helps you to get rid of the “Fatal error: Out of memory”:

1. Before you start updating WP … don’t forget database update!
2. Deactivate the active WordPress-Plugins in the admin section under “Plugins”.
3. Now, you can start the automatic update of your WordPress installations.
4. Now it’s possible to reactivate the deactivated plugins: Select “Plugins” and “Recently Active”.

The WordPress community and your own blog readers will enjoy a new level of cyber secrity